Electromagnetic device



J. A. WOTTON.

ELECTROMAGNETIC DEVICE.

APPLICATION FILED AUG.29,1917- 13673727. Patehted Feb. 8,1921.

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UNITED STATES PATENT OFFICE.

JAMES A. WOTTON, OF MONTGLAIR, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRICCOMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

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To all whom it may concern:

Be it known that I, JAMES A. WOTTON, a citizen of the United States,residin at Montclair, in the county of Essex and tate of New Jersey,have invented certain new and useful Improvements in ElectromagneticDevices, of which the following is a full, clear, concise, and exactescription.

This invention relates to el ctromagnetic devices. and more particularlyto electromagnetic circuit controlling devices or relays havingretractable armatures.

In most cases where such devices are employed, it is desirable that theyshall operate at substantially the smallest possible value ofmagnetizing force for a given structure, in order to minimize the energylosses therein. In other classes of service, it is desirable andimportant to reduce the difference between the'operating and releasingcurrents in such devices to a minimum in order to improve the commercialrange of operation.

The general object of this invention is to provide an electromagneticdevice orrelay such that for a given magnetic structure, a minimum valueof magnetizing force will be requi ed to actuate it, and wherein thereleasing magnetizing force is only slightly below that required for itsactuation.

Generally considered, an electromagnetically operated device embodyingthe present invention is characterized by the provision of means wherebythe actuating flux path is subjected to auxiliary magnetization,

for the PHIPOSGXOf decreasing the difference between the actuating andreleasing current values of the device. More specifically considered,the invention is characterized by the provision of means wherebytheactuating flux path of an electromagnetically-operated device issubjected to the auxiliary magnetization effect of alternating current.Still more specifically considered, as applied to anelectromagnetically-operated device, the invention is characterized bythe provision of means whereby alternating current is passed through thecore of the electromagnetic structure for the purpose of magnetizing theactuating flux path.

This invention will be more clearly understood by reference to thedrawings, in which Figure 1 is a schematic representation of anelectromagnetic device or relay with its associated source of energizingcurrent, show- Specification of Letters Patent.

\ Application filed August 29, 1917. Serial No.

Patented Feb. 8, 1 921.

ing one embodiment of this invention; Fig. 2 1s a graphlcalrepresentation showing the relation between the current in theenergizing winding of the device of Fig. 1 and the flux produced therebyin the magnetic circult under both the ordinary operating conditions andunder the more exacting conditlons satisfied by this invention; Fig. 3

shows graphically the relation between the 11, whereby the core isenergized to attract the armature 6, to close a contact between Iconductors 12 of an auxiliary circuit. Upon the deen'ergization of thecore 5, the armature 6 is retracted by the force of gravity to open theauxiliary circuit. A source 0 alternating current 13 of suitableamplitude core 5, whereby alternating current is caused to passlengthwlse through the core. Nonmagnetic members 14:, 14 serve asterminal supports and spool heads for the winding 8, while the stud-15and nuts 16 act as backstop and adjusting means for the armature 6. a

l The effect of an alternating current passing through the core upon themagnetic characteristics thereof will be more clearl understood byreference to Fig. 2. Graph X is the magnetization curve obtainedbypassing successively increasing'values of current through the winding8 of the relay of Fig. 1,- and measuring the corresponding values ofmagnetic flux in the core. Graph B is a similar magnetization curveobtained from the same core, while alternating current from the source13 ispassing therethrough. This characteristic behavior of ma eticmaterial is discussed by Professor Ewing in his book on the MagneticInd/action in Iron and Other Metals. The effect of the phenomenonrepresented by the magnetization curves of Fig. 2 is that a givencurrent value a will normally produce a value of flux 6, while a largerflux value, represented by 0, will result if an alternating current isand frequency is connected in series with the passing through themagnetic material of the core. Or, viewing it from another angle, asmaller value of current (Z, when alternating current is flowing, willproduce the same amount of flux b as is normally produced by a currentof value a.

Referring now to Fig. 3, the curve C corresponds to the initialmagnetization curve A of Fig. 2. D and E are successive branches of acurve similar to the wellknown magnetization loop obtained by cyclicmagnetization of magnetic material. F corresponds to the magnetizationcurve B of Fig. 2, and furthermore represents the two branches of themagnetization loop which have become merged into one, due to thealternating current passing through the core. Only those parts of thesecurves which indicate the actual pull on the armature when the relay isin use are shown in full lines. The remaining portions, represented bydotted lines, are shown merely for clearness of description.

Let it be assumed that a pull on the armature represented by e isnecessary to attract it from its retracted position, while a pull 7' isrequired to hold it in actuated position. If no alternating current ispassing through the core, a value of direct current it would be requiredto actuate the armature; the maximum value attained by the current asdetermined by the battery 9, and resistance 11 being represented by 9.Upon opening the circuit at key 10 or upon increasing the value of theresistance 11, in series with the battery 9, the currentwill fall andthe armature will remain attracted until the current has reached thevalue 91, whereupon the pull is reduced to the releasing value 7,allowing the armature to fall back into retracted position. Thecorresponding current values required when the alternating current ispassing through the core, are 70, g and m.

It is, therefore, clear that while the maximum energizing current,determined by operating conditions, may be the same in either case, thearmature will first be attracted by a substantially smaller value ofenergizing current, when alternating current is flowing and will beretracted, on the other hand. at a substantially higher value. Themargin of operation, which in either case is determined by the ratio ofreleasing current to operating current is substantially higher when thealternating current is passing through thecore, as shown by the ratio ofm to is as compared with n'to it.

There would be in practice a slight dis continuity in the curves of Fig.3 at the point where the armature changes from its retracted position toits actuated position, and vice versa, due to the consequent change inreluctance of the magnetic circuit; but

for the purpose of simplicity such slight discontinuity has not beenshown.

It is obvious that many modifications of the-exact structure shown inFig. 1 of the dra-wingmay be made, all of which come within the scope ofthis invention. Currents having other characteristics than thosedescribed may be used to actuate the armature and means other than thosedescribed may be used to produce auxiliary magnetization of theactuating flux path.

What is claimed is: r

1. The method of decreasing the difference between the actuating andreleasing operating current values of an electromagnetically operateddevice which consists in auxiliarly magnetizing the magnetic circuitduring the application of the operating current.

2. The method of decreasing the difference between the actuating and thereleasing current values of a direct currentelectromagnetically-operated device, which consists in magnetizing themagnetic circuit by means of alternating current during the applicationof the direct current.

3. In an electromagnetically-operated device, an energizing winding, .amagnetic circuit therefor including a retractable armature cooperatingtherewith, means for supplying operating current to said winding, andmeans for simultaneously producing auxiliary magnetization of themagnetic circuit.

4.-In an electromagnetically-operated device, an energizing winding, amagnetic circuit therefor including a retractable armature-cooperatingtherewith, means for supplying operating current to said winding,andmeans for simultaneously producing auxiliary magnetization of themagnetic circuit by means of alternating current.

5. In a direct current electromagneticallyoperated device, an energizingwinding, a magnetic circuit therefor including a retractable armaturecooperating therewith, means for supplying direct current to saidenergizing winding. and means for simultaneously magnetizing themagnetic circuit by means of alternating current.

6. In a direct current electromagneticallyoperated device, an energizingwinding, a magnetic circuit therefor including a core and an armaturecooperating therewith, means for supplying direct current to saidenergizing winding. and means for simultaneously passing alternatingcurrent through said core for the purpose of magnetizing the magneticcircuit.

I In witness whereof. I hereunto subscribe my name this 23rd day ofAugust A. D., 1911.

JAMES A. WOTTON.

